Problem with a 30 volt 20 amp variable power supply. Repair help.

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mramos1

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I bought a HY3020 power supply years ago. Stored it and forgot all about it. Just powered it up and it works for a bit then it shuts down. I loose power all the way back to the opto and SCR. A feedback loop I guess, but this thing is beyond me for sure.

Anyone feel like giving a hand. Been years since I have touched any real circuits (esp analog). I have the schematic and will attach it. I have a small PS, but would like the extra amps if this one can be figured out. Just a random shutdown is a pain to trouble shoot. But willing to perform tests here if any takers.
 

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How old is the device?

Can you check the voltage of C006 and C007 carefully while it's powered up? First both on anode (+) and kathode(-) pins then try to measure from the anode pin of C006 and kathode pin of C007 since they are connected in serial. Do the same when it goes off itself while the switch is closed (device turned on)

Be careful since those are the load-caps ! If you are not experienced you might harm yourself!

I guess something is making the device collapse after a certain time. This is mostly caused by caps or after a component gets hot.
 
I will look for a date code on a chip (there is a SMT 082 on a sip card). I bought it maybe 8 years ago.

When I get home I will measure across C6 and C7 together and each separate, working and in failed state. I have a 12 volt 150 ma load on it and it runs for minutes. Thanks for the help.
 

C006 and C007 each are a pair of paralleled 820uF 250vdc caps.

With the load working C6 is 156.8vdc, C7 is 156.2, both are 313.5

With display off and no power out switch on. C6 is 158, C7 is 157.2 and both 315.2

Mike
 
mramos1 said:
C006 and C007 each are a pair of paralleled 820uF 250vdc caps.

With the load working C6 is 156.8vdc, C7 is 156.2, both are 313.5

With display off and no power out switch on. C6 is 158, C7 is 157.2 and both 315.2

Mike
Click to expand...

Alright so (we guess) no faulty there, next try to measure the - pin of C105 and + pin of C104, you should measure around 10V there. If it's so, it is fine too.
Next C406, should be 30V. Next check C2, C10, R2 and R10 if 5V available. Does the device has any stand-by mode functionality?

But if only the display turns off then it might be the IC1 or IC2 aswell, check also if you have the 5V after it goes off.
 

I found -C105 to +c104 25.3 volts on and off if I recall. c406 was 12.3vdc (not 30vdc) ON and when off 1.2vdc (switch on)

No standby or buttons.

Could not find C10 or R2 will look when home. Did find C2 but hard to check.
 
What I have across the parts with it working (first image). display on and driving a 12volt load. All shows mvolts there when it cuts out.



On the 30V there was 12.3v on and working (display and power out), and 1.1v when it blanked display and no output
here across c406.
 
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Alright so I found out that the TOP223 is actually a Three-Terminal Off-Line PWM Switch and it says in the datasheet (link):
"If the CONTROL pin total external capacitance (CT ) should discharge to the lower threshold, the output MOSFET is turned off and the control circuit is placed in a low-current standby mode. The high-voltage current source turns on and charges the external capacitance again. Charging current is shown with a negative polarity and discharging current is shown with a positive polarity in Figure 6. The hysteretic auto-restart comparator keeps VC within a window of typically 4.7 to 5.7 V by turning the high-voltage current source on and off as shown in Figure 5(b). The auto-restart circuit has a divide-by-8 counter which prevents the output MOSFET from turning on again until eight discharge-charge cycles have elapsed. The counter effectively limits TOPSwitch power dissipation by reducing the auto-restart duty cycle to typically 5%. Auto-restart continues to cycle until output voltage regulation is again achieved."

We see that the C102 is the external cap here. If I would guess, I would say that either the external cap is faulty and never reaches the full charge-discharge step so the device won't turn on again after a certain time ("which prevents the output MOSFET from turning on again until eight discharge-charge cycles have elapsed") or the TOP223 might be faulty. Atleast you know where to measure now. Compare the voltages on TOP223 and after it shut down itself.




Because I assume that there must be always the +5V so the optocoupler is permanently on and the cap should stay charged which should cause the TOP223 to stay on always. Just a guess but try your luck.

Edit: is the +5V still present after it shut down itself?
 
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simpleGuy said:
is the +5V still present after it shut down itself?
Click to expand...

Not it all when off.

The TOP223 might be hard to find, the cap I have. The TOP IC might kill the idea, but never know.

Even with the no 30VDC and the missing -5v, when it runs, it power the external load just fine.

Thanks again for the quick help. I have not done hardware for a LONG time...
 


Well it will take time but then you have to go step by step, you have the schematic which is good and the voltage values what it should be, follow the voltage and check at/after which component it drops/collapse. It's an old device, might be a dried/faulty cap or something else.
Good luck
 

Will give it a shot. I am a lot closer then I was. I bought it years ago and it did this when I bought it. I hope a bad cap. I might shotgun the cap (easy to get too and have them). Will post results.
 
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here is what I have so far. Looks like one side drops out (fig. 2). When it starts (and works), it goes from 11v and slowly bleeds down to .2mV on all the points.



 
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The TOP223 looks like it stops oscillating. Could be a defective TOP223 or it could be the TOP223 operating properly and shutting down with an overload. Might try disconnecting H1 and H2 (lift one end of D105 & D108) and see if the +/- 5 volts stay up.
 
Ylli. I pulled the diodes and caps D105 and D108 (caps were piggy backed in sam holes). Got the +5 and -5 from U+ (transformer pin 10). So that is good.

does that tell the circuit area of the bad part? I did not put them back in yet. The cap and diode pins are in 1 hold on the PCB. Want to make sure OK to put them back in.
 
There are two subcircuits there, H1 feeds one and H2 feeds the other. I don't pretend to be an expert on switching supplies, but from where you are at I would try reconnecting H2 by reinstalling D108 (and it's cap). Fire it up and see if it that +/- 5V continues to operate.

If it does not, then the section driven by H2 has some problem. If it does, then the section powered by H1 may be the issue, and that would be the place to look.
 
Looking at the data sheet, the only way the control pin of the TOP223 can still have 6V on it with no voltage across the LED is if the U101 optoisolator transistor is leaky or shorted; or Q101 emitter is open circuit?

Check the base voltage on Q101; if that's less than 1V, try replacing the opto isolator.

Or the TOP223 has failed - but if that was the case, the 9V bias circuit that feeds the opto should also be dropping out?
 
Ylli, good day..

H1 out R105 and r108 h2 in, +5(opto) and -5 there until it display/power drops out. Then -5 stays D109/R102 but opto 1 and 2 are mvolts. Opto pin 3 is 5.5v and pin 4 is 6.7v. opto all from Transformers pin 5

rjenkinsgb, thanks for looking I have .6v on Q101 base.

I have other opto, maybe 4 pin ones with the same specs.
 
Ignore my last post, I misinterpreted your reply......

So with D108 reinstalled and D105 still out, the unit shuts down. How long does it take before it shuts down?

See the attached. Connect the negative voltmeter lead to the point shown in black. Connect the positive meter lead to the point indicated +1. Turn the unit on. Before it shuts down, what do you measure for voltage?
Now move the red lead to +2. What is the voltage there (before it shuts down)?
 
I hooked both back up R108 and R105. But have 44vdc cross C106. 24vdc to r414 from - c106. But H1 and H2 hooked back up. That OK

Also when it cuts out (5-10 minutes) 58 volts and a slow drop on R414 and cap +
 
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